1. Field of the Invention
The present invention relates to a heterogenous catalyst particularly suited to the metathetic reactions of olefins.
2. Description of the Related Art
Such a heterogeneous catalyst conventionally comprises a support, consisting of an inorganic oxide or a mixture of inorganic oxides, and a tungsten compound bonded to the surface of the support.
The terms metathesis, disproportionation or dismutation are used to refer to a catalytic reaction in which asymmetric olefin molecules are converted to new olefins having a hydrocarbon chain longer or shorter than that of the precursor olefin. Thus, propene for instance reacts in the presence of said catalysts to form ethene and butene. Further, two different kinds of olefin molecules can react in a metathetic manner exemplified by the reaction of ethene and 2-butene forming propene. Other areas of application of metathetic catalysts are, e.g., disproportionation by ring opening, and the utilization of olefins having a carbon number of less than 10 and more than 20 that result from the oligomerization of ethene by way of first isomerizing them into i-olefins and then allowing them to react mutually in the presence of a metathetic catalyst. Another utilization method of said olefins is to allow them to react after isomerization with ethene in the presence of a metathetic catalyst to produce odd-carbon .alpha.-olefins, from which fractions suitable for raw materials for making lubricants can be separated by fractionation.
Catalysts for metathetic reactions are today prepared by conventional methods, which include the impregnation of a support with a precursor of the active metal species from a solution of the metal salt, the co-precipitation of the metal salt and the support material and the coextrusion of the support and the precursor of the catalyst. Generally, an essential step in the preparation of the catalyst also comprises the activation of the catalyst by heating at an elevated temperature in the presence of air or an inert gas. Typical catalysts of this kind include the oxides of Re, W and Mo on a silica gel or alumina support, or on a mixture-type support.
The above-described preparation methods of heterogeneous catalysts are poorly suited to control the bonding of the active catalyst materials onto the support material surface (that is, the control of the dispersion of the catalyst).
The surface of the powdered particles in support materials used in heterogeneous catalysts is structurally inhomogeneous. Therefore, the methods of the conventional technology are poorly suited for a controlled bonding of a metal species or metal compound.